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Old 04-16-2018, 11:59 AM   #61
SEA_ARCHER
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Re: Double Roller Trigger for Pathos handle, Ermes Sub

There is definitely wear on the back roller. I am not sure if it is from regular use or from the time I tried to load it when the roller was skewed. Like I said i noticed it didn't load and tried maybe once a little harder to load before I realized it may have skewed like others had mentioned. I took the trigger out of the gun to inspect the parts and The front roller didnt spin as easily after all those hot banded shots either. The back roller has several marks in it. There are more than could have been made from the rear roller skewing one time. There is a possibility it was slightly skewed on other loading sequences and I just didn't notice any difficulty. All other times the shaft engaged in the trigger quite easily.

Still have high hopes. It seemed great until the pressure from hot bands.

Last edited by SEA_ARCHER; 04-16-2018 at 12:40 PM.
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Old 04-17-2018, 12:55 AM   #62
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Re: Double Roller Trigger for Pathos handle, Ermes Sub

Hmmm ... that is not good. Thanks for the feedback! I have to admit that I had my doubts about the floating roller working well once loaded up .... I mean it is rotating off axis and it is really difficult to predict how that affects rotation. But Mario said he was using that trigger on a modified double roller box with 3 bands with no problems. The thing is that it is really difficult to know if the front roller is rotating or if it is not. If it is not, then this just works like a friction trigger and thus is vulnerable to scratching or galling. You will get a few good shots, but once the scratches start happening the break off point will not be predictable ... and that means accuracy goes down hill. Even if the break is identical each shot, but the break is in different locations of the trigger pull ... the accuracy will drop dramatically. I can see that when testing on a target in the pool. The shots start "walking" off target as the trigger gets scratched.

As for the back roller scratches, it looks like this is just 316 roller and not 17-4 hardened ... this of course should be changed to 17-4 as this is much harder and will resist hard shafts better. But to be honest the scratches on the back roller will not affect performance, so I wouldn't worry about that. More important is dealing with the front roller and making sure that it turns properly and predictably.

I do have a drawing for a mini 6.6 roller sear similar to the double roller, but this would need to be CNC cut (expensive). The roller on that would be about 20% smaller than what is on the double roller ... but for 2 hot bands such as the Pathos 130 ... it should be plenty strong enough. I couldn't get Mario interested in that trigger as it just costs too much to make and he doesn't think it would sell. I might make a few of those sears just to try out the idea. Another possibility is just to use a .25" plate to cut the sears ... this comes out to be about 6.35mm ... and you could laser cut the sear and then you just need one CNC front cut for the front roller. But at 6.35mm the roller would be a little smaller than at 6.6 ... but by using a hardened trigger sear it should be more than strong enough. I think C4 uses a very small front roller and it seems to work ok. At least the double roller system is well tested and there are several thousand of those triggers in use today ... so we know it works well.
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Old 04-17-2018, 01:53 AM   #63
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Re: Double Roller Trigger for Pathos handle, Ermes Sub

I don't want to sound the least bit know-it-all'ish but when I saw the front cradle design I have to admit, I was slightly confused. The thing that caught my eye was that the area of contact is so much bigger at the roller to cradle point than it is from roller to trigger. In my thinking, that could lead to a lot of friction, which could possibly be what is happening here.
I am with Majd, that it makes sense to try to make that roller sit "properly" on a pin, instead. Either way, I hope and trust Mario will get it right:-)

Majd, a manufacturing question: I understand the need for a second operation to cut a vertical slot in the sear for a roller to sit in with a pin. But is there any reason you can't do this on the laser, too? Couldn't you take the cut out sears, turn them 90 degrees and place them in a jig for that second cut-out or will the heat potentially warp the part and throw it off tolerances? I know the fixture would have to be manufactured, too and possibly on CNC, but that's a one time expense.

Last edited by Diving Gecko; 04-17-2018 at 02:38 AM.
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Old 04-18-2018, 01:28 AM   #64
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Re: Double Roller Trigger for Pathos handle, Ermes Sub

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Originally Posted by Diving Gecko View Post
I don't want to sound the least bit know-it-all'ish but when I saw the front cradle design I have to admit, I was slightly confused. The thing that caught my eye was that the area of contact is so much bigger at the roller to cradle point than it is from roller to trigger. In my thinking, that could lead to a lot of friction, which could possibly be what is happening here.
I am with Majd, that it makes sense to try to make that roller sit "properly" on a pin, instead. Either way, I hope and trust Mario will get it right:-)

Majd, a manufacturing question: I understand the need for a second operation to cut a vertical slot in the sear for a roller to sit in with a pin. But is there any reason you can't do this on the laser, too? Couldn't you take the cut out sears, turn them 90 degrees and place them in a jig for that second cut-out or will the heat potentially warp the part and throw it off tolerances? I know the fixture would have to be manufactured, too and possibly on CNC, but that's a one time expense.

To cut many parts out of a single laser pass can be done very very quickly and efficiently. To take an individual part and put it on a custom jig and check that tolerances are extremely high and only then do the CNC cut ... well it is very time consuming and not easy to automate. You reach a point where it is just as expensive to cut the entire sear via CNC. I think this could easily be automated using Swiss Screw CNC machines as these machines are programmable lathes that can also do horizontal cuts ... but for some reason all the shops that have these machines just use the extra efficiency to make more profit, and prices are also high. It all boils down to cost. Will someone pay an extra $15 or $20 for a trigger? I certainly would and probably several people in this forum that understand the problems also would. But I can tell you that I have had discussions with trigger designers from major spearfishing companies and they still have no clue that the galling in triggers can cause a huge drop in accuracy. They figure so long the trigger shoots it should be fine.

Of course there is always the alternate system I mentioned earlier ... that really will transform how all triggers are made and do it much cheaper. But my guess is that without a patent this would easily be copied. Mario still thinks the front roller system will work well and just yesterday he sent me the latest drawings and I put them on a computer and simulated the action. According to the simulation the back roller problem is fixed, but there is no real good way to simulate the rotation of the front roller as it is off center and not on an axis. Even if there was proper data for that, I would not feel comfortable with it unless it was tested in real firing conditions with at least 500 shots. In the pool it is very easy to verify if the trigger is not shooting accurately as the shot groupings will tend to move around ... plus I have shot so many shots that I can feel the trigger pull is different. The floating front roller can still possibly work well even at high loads, but IMHO this has to be proven in testing before it becomes something that is sold to the public.
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Old 04-18-2018, 02:27 AM   #65
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Re: Double Roller Trigger for Pathos handle, Ermes Sub

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Originally Posted by spearq8 View Post
To cut many parts out of a single laser pass can be done very very quickly and efficiently. To take an individual part and put it on a custom jig and check that tolerances are extremely high and only then do the CNC cut ... well it is very time consuming and not easy to automate. You reach a point where it is just as expensive to cut the entire sear via CNC. I think this could easily be automated using Swiss Screw CNC machines as these machines are programmable lathes that can also do horizontal cuts ... but for some reason all the shops that have these machines just use the extra efficiency to make more profit, and prices are also high. It all boils down to cost. Will someone pay an extra $15 or $20 for a trigger? I certainly would and probably several people in this forum that understand the problems also would. But I can tell you that I have had discussions with trigger designers from major spearfishing companies and they still have no clue that the galling in triggers can cause a huge drop in accuracy. They figure so long the trigger shoots it should be fine.

Of course there is always the alternate system I mentioned earlier ... that really will transform how all triggers are made and do it much cheaper. But my guess is that without a patent this would easily be copied. Mario still thinks the front roller system will work well and just yesterday he sent me the latest drawings and I put them on a computer and simulated the action. According to the simulation the back roller problem is fixed, but there is no real good way to simulate the rotation of the front roller as it is off center and not on an axis. Even if there was proper data for that, I would not feel comfortable with it unless it was tested in real firing conditions with at least 500 shots. In the pool it is very easy to verify if the trigger is not shooting accurately as the shot groupings will tend to move around ... plus I have shot so many shots that I can feel the trigger pull is different. The floating front roller can still possibly work well even at high loads, but IMHO this has to be proven in testing before it becomes something that is sold to the public.
Thanks for elaborating. I was hoping that if the jig was precise and holds enough parts (sears) it could still be doable and feasible pretty much by dropping and locking in the parts. I don't think they would zero the machine on the parts, only once on the jig before doing the run, if that, so it shouldn't really take long. But I just realized that parts coming off a laser may need to be deburred before they would sit 100% precisely in a jig, anyways.
Come to think about it, often big production runs actually prefer to use a second, or third, machine for subsequent operations.
I had this chat with an engineering friend of mine who had 5 axis CNC mills at her disposal for their very 3D intensive machining. But they would rather run the parts on two or three 3 axis machines. Just move the parts from one machine, flip them over onto the fixtures in the next and so forth.
But either way, I can see how that becomes expensive on small parts without much room for profit.
No need to entertain my speculations any further, I was just curious and thanks again:-)
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Old 04-19-2018, 12:09 AM   #66
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Re: Double Roller Trigger for Pathos handle, Ermes Sub

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Originally Posted by Diving Gecko View Post
Thanks for elaborating. I was hoping that if the jig was precise and holds enough parts (sears) it could still be doable and feasible pretty much by dropping and locking in the parts. I don't think they would zero the machine on the parts, only once on the jig before doing the run, if that, so it shouldn't really take long. But I just realized that parts coming off a laser may need to be deburred before they would sit 100% precisely in a jig, anyways.
Come to think about it, often big production runs actually prefer to use a second, or third, machine for subsequent operations.
I had this chat with an engineering friend of mine who had 5 axis CNC mills at her disposal for their very 3D intensive machining. But they would rather run the parts on two or three 3 axis machines. Just move the parts from one machine, flip them over onto the fixtures in the next and so forth.
But either way, I can see how that becomes expensive on small parts without much room for profit.
No need to entertain my speculations any further, I was just curious and thanks again:-)
All the machine shops work on having large numbers done automatically and without intervention. The "tooling" would be to setup up the machine once and let it run automatically. This means that if you have to manually remove the part for further processing the tooling cost goes up dramatically. Machining is not the only way to mass produce metal parts, you can of course use some sort of precision investment casting or even Metal Injection Molding ... but then the costs of creating a mold and preparing it for casting are very high. You would need a production of say 3,000 to 5,000 pieces before the costs get factored in and it becomes cost effective. The other problem is that once you make the mold you cannot really change things and if you do change or tune the design, you would need a new mold.

On my computer I can quickly put together a perfect trigger ... the challenge for Mario is not to have the perfect design, but rather to manufacture that design where it becomes cost effective to the end user ... that is the big challenge.
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